Sinlge Polarization Photonic Crystal Fibers

Photonic crystal is introduced at the end of 1980's as a kind of novel concept and material, to date, having had a great progress in theory and application. Photonic crystal fiber is a novel fiber which the structure of photonic crystal is applied to fiber.Photonic crystal fiber having became great interested in international research as a novel fiber, because it holds many transmission characteristics that is unmatched by traditional fiber. Such as, endless single mode character, flattened dispersion, high nonlinear, ultra-high birefringence, large mode area, single polarization effects.Photonic crystal fiber has two kinds of light-guided mechanism: One is improved total internal reflection Photonic crystal fiber, or index guiding, and It's light-guided mechanism is similar with the traditional fiber. For refractive index of the core compared to the surrounding media is higher, light-wave is guided by total internal reflection; The other is photonic band-gap fiber, which guide-light mechanism is very different with the traditional fiber. Light can not be propagated in PBGF if its frequence falls into the band gap.It is very difficult to achieve a closed analytical solution for a PCF due to its complicate structure, then an accurate numerical simulation is very important to analyze light-guided characters and design structure parameters. Of all the numerical methods, Frequency domain finite difference method(FDFD) is characterized with its simplicity, reliability and efficiency, so the propagation constant |3 and distribution of each mode filed can be calculated at gave structure and electromagnetic parameters of optical waveguides.In this paper, The compact 2D-FDFD is applied to have researched birefringence and single polarization effect of PCF. One can obtain high birefringence due to a sharp index contrast between air and silica in photonic crystal fiber. We proposed a kind of high birefringence polarization maintaining fibers based on the photonic crystal fibers, in which the birefringence can be much higher than the conventional ones. Influences of structure parameters and incident wavelength on the birefringence are analyzed. Research results provide important basis which is used to design polarization maintaining fiber and single polarization fiber.